Motion converting mechanism



y 1944- F. A. TRUESDELL 2,349,314

MOTION CONVERTING MECHANISM "Original Filed Sept. 27, 1937 2 Sheets$heet2 7* 28 50 x 1 ATTORNEYS Patented May 23, 1944 MOTION CONVERTINGMECHANISM Fred A. Truesdell. deceased. late of East Cleveland, Ohio, byJetta Truesdell, administratrix, East Cleveland, Ohio, assignor ofone-half to Wilmer S. Fallon, Cleveland, Ohio Original applicationSeptember 2'7, 1937, Serial No. 166,032. Divided and this applicationFeloruary 25. 1942, Serial No. 432,342

13 Claims.

This invention relates to motion converting devices for convertingrotary into reciprocating motion or vice-versa, and aims to provide asimple and efiicient construction for a device of this kind which can bereadily embodied in a pump, engine, or hydraulic motor.

Another object of this invention is to provide an improved constructionfor a device of this kind having cooperating cam and follower elementsand in which the cam and follower elements are shaped to cooperatesubstantially without backlash, vibration, or shock and with arelatively increased area of contact at the points of maximum load so asto minimize wear.

A further object of the invention is to provide an improved constructionfor a conversion device of the character mentioned having a cam elementin the form of an endless generally elliptical ridge lying in a planeextending oblique to the rotation axis, and in which the width and sidefaces of the cam ridge are such that a cam follower having opposedsubstantially frustoconical bearing portions will cooperate therewithwith minimum wear and substantially without backlash. vibration, orshock.

Still another object of this invention is to provide an improvedconversion device of the character referred to in which the cam elementis integral with and generated on a cylindrical metal body.

Yet another object of this invention is to provide an improvedconversion device of this character in which the integral generated camelement is on the inner surface of a cylindrical metal sleeve.

It is also an object of this invention to provide a conversion device ofthe character referred to in which the cam and follower are of such formthat the follower has simple harmonic motion.

Other objects and advantages of the invention will be apparent from thefollowing description when taken in conjunction with the accompanyingsheets of drawings, in which:

Fig. l is a partial longitudinal sectional view taken through a motionconverting mechanism embodying the present invention;

Fig. 2 is a transverse sectional view taken through such mechanism online 2-2 of Fig. 1:

Fig. 3 is a detached end view of the cam sleeve;

Figs. 4, 5, and 5 are longitudinal sectional views taken, respectively,on lines l i,-55, and 6-6 of Fig. 3;

Fig. 7 is a diagram showing the form of the primary and. secondarysecant planes as pro- ,iected from the oblique or secant planes Ia-4aand lb-lb of Fig. 4, said diagram also illustrating the generallyelliptical shape of the cam;

Figs. 8 to 11, inclusive, are partial sectional views taken through thecam at 30 intervals, as indicated in Fig. 4, and showing theprogressively changing cross-sectional shape of the cam;

Fig. 12 is a larger scale sectional view through the cam adjacent itspoint of minimum width and maximum load and showing the relativelyincreased area of contact between the cam and follower; and

Fig. 13 is a sectional view similar to Fig. 4, but showing adouble-throw cam.

This application is a division of application Serial No. 166,032 filedSeptember 27, 1937.

In Figs. 1 and 2 the motion conversion mechanism of the presentinvention is shown as being embodied in a machine Ill having a housingll provided with a cylindrical chamber [2 in which a rotor l3 operates.The rotor may be sup ported for rotation by suitable bearings l4 and mayhave a shaft portion l5 which projects through the cover It of thehousing. The motion converting mechanism comprises a cam 11 connectedwith or carried by the housing and one or more cam followers i8reciprocatably slidable in the rotor l3.

The rotor it may comprise an elongated body having a plurality ofguideways or cylinders l9 in which the cam followers l8 operate. Thecylinders or guideways l9 may extend axially of the rotor 13 insubstantially parallel relation and may be arranged in an annular serieswhich is concentric with the rotation axis, as shown in Fig. 2. Therotor portion i341. which is nearest the housing cover I 8 may be ofrelatively reduced diameter and the guideways 19a, which are formed onthis reduced rotor portion as continuations of the guideways l9, may besubstantially semi-circular instead of complete or full cylinders.

The cam I"! may be carried by a substantially cylindrical member orsleeve 2!] which extends into the housing so as to surround the reducedportion 57in. of the rotor. The bearing Ma supporting the rotor may besuitably mounted in the housing H, or, as shown in this instance, bemounted in the cam sleeve 29. The form of the cam ll will be describedin greater detail hereinafter, but as seen from Figs. 1 and 3, comprisein general an endless elliptical ridge projecting from the inner surfaceof the cam sleeve 20 and lying in a transverse or secant plane extendingobliquely to the axis of rotation of the rotor IS. The cam I! hasconverging side faces 2i and 22 and a top face or land 23. The camfollower l8 has a cam-engaging portion in the form of a notch or groove2% in which the cam ridge I! engages. This notch or groove is defined bytwo opposed substantially frustoconical bearing portions 25 and 26 whichengage the side faces 2| and 22 of the cam and are connected by thereduced cylindrical portion 21 which engages the top face or land 23.

From the arrangement thus far described, it will be seen that whenrelative rotation occurs between the rotor l3 and the cam sleeve 20, thegrooves or notches 24 of the followers l8 will traverse the cam I! andthe followers will have reciprocating movement in the guideways I9 andMia. As representing a practical embodiment of the motion convertingmechanism herein disclosed, copending application Serial No. 454,773,filed August 14, 1942, shows such mechanism embodied in a fluid pump ormotor. The machine In may be a pump, or may be a hydraulic motor orengine. When the machine is operated as a pump, power is applied to theshaft portion l of the rotor [3 while the cam sleeve is held stationaryand the relative rotation between the rotor and cam sleeve producesreciprocation of the followers l8, which then operate as plungers in thecylinders I9 to create pressure or displacement in the fluid beingpumped. When the machine is operated as a hydraulic motor or engine,fluid pressure acts on the cam followers lli, which then serve aspistons, and the pressure of the followers against the stationary cam llproduces a reaction in the rotor I3 causing rotation of the rotor andthe shaft l5. Obviously if the rotor were held stationary the pressureof the followers against the cam would cause rotation of the cam andhousing. In either case it will be seen that the cam i1 and thefollowers 8 cooperate to convert rotary into reciprocating movement orvice-versa.

The form of the cam IT can be best described by reference to Figs. 4 to11, inclusive, from which itwill be seen that the cam projects as anendless or generally elliptical ridge extending around the inner surfaceof the cam sleeve 20 and lying sub stantially in a secant plane lalawhich is oblique to the rotation axis and may intersect the. latter atan angle of approximately 45. The cam ridge has a cross-sectional shapecorresponding substantially with that of a truncated isoceles triangleof which the side segments form the working faces 2! and 22 of the cam.The generally elliptical shape of the. cam is represented by the ellipseof Fig. 7 which has been projected from the secant plane lala asindicated by the projection lines 3ila.

The cam ridge is of varying width or axial thickness, as shown in Figs.4, 5, and 6, and varies progressively from points of maximum thicknesslocated at the ends 28 and 28 of the major axis of the ellipse 30 topoints of minimum thickness 3| and 32 located at the ends of the minoraxis of the ellipse. It is apparent from Figs. 1 and 2 that the pointsor sections of maximum thickness may be referred to as idling points orpoints of dead center because the reciprocating or axial movement of thefollower it reduces to Zero when these points or sections are traversedby the camengaging portion of the follower. The cam points or sections3! and of minimum. thickness may be. referred to as the working sectionsof the cam because they impart maximum reciprocating or axial movementto the follower and are subjected to the maximum working pressure whenthese sections are traversed by the cam-engaging portion of thefollower.

The above-mentioned secant plane l'ala may be referred to as the workingplane or primary secant plane because it extends through orsubstantially through the four midpoints of the cam which arerepresented by the points 28, 29, 3|, and 32. The points 28, 29, 3|, and32 are imaginary points within the cam spaced apart and lyingsubstantially midway between its working faces 2'! and 22 and atsubstantially the midpoint of the height or altitude of the cam.

A second oblique or secant plane 'Ib--1b is shown in Fig. 4 and may bereferred to as the plane of cam generation or the secondary secantplane. This secondary plane extends at a somewhat smaller angle ofobliquity than the primary plane la'|a and contains the locus of themidpoint 21a of the reduced portion or neck 21 of the follower if! asthe latter rolls around on the cam. This locus describes an ellipse 33on the secant plane lb-4b corresponding substantially with the ellipse33 of Fig. 7 which has been projected on the lines 33a.

The cam ridge IT may be formed in various ways, but is preferablygenerated on the inner surface of the cam sleeve 2!! about itslongitudinal axis A by means of a rotating and revolving axially movabletool or cutter, such as a milling cutter (not shown), having a contoursubstantially identical with the cam-engaging portion of the followerl8. By causing such a tool or cutter to follow the outline of theellipse 33 in the secondary secant plane Tblb, the cutter will generatethe cam I! about the longitudinal axis A of the cam sleeve 20. When thecam ridge is formed in this way, it will be found that the convergingsides or working faces 21 and 22 will be substantially straight or flatat the relatively wide sections 23 and 29 and will be concavely curvedat the relatively narrow sections 3! and 32. At points between theserelatively wide and relatively narrow sections of the cam ridge, thesides or working faces will vary progressively in shape as representedby the sections or profiles illustrated in Figs. 9 and 10, and thecurved side faces of the relatively narrow sections of the cam willmerge smoothly into the relatively straight or fiat side faces of therelatively wide sections of the cam.

It will be readily seen that when the cam H has the form above describedand is generated in the manner explained, the follower or followers l8cooperating with such cam will have a true simple harmonic motion. Thisis highly desirable in a motion converting device of this characterbecause it affords greater efficiency and smoother operation. By varyingthe obliquity of the secant planes la-la and lb-lb from the angles shownin Fig. 4 the stroke or throw of the follower Hi can be varied asdesired and its reciprocating movement will in all cases still be simpleharmonic motion.

It is important to note that the frusto-conical bearing portions 25 and26 of the follower 18 will have substantially a line contact with thestraight sides 24 and 22 of the relatively wide sections of the cam andwill have contact portions of a relatively larger area when thesefrusto-conical bearing portions engage the concave sides of therelatively narrow sections 3| and 32 of the cam. In other words, at thepoints of engagement of the follower with the cam [1 corresponding withminimum load. the contact will be substantially a line contact, but whenthe follower engages the cam at the points of maximum load, the contactarea will be substantially greater than a line contact and will havesubstantially the shape and area of the contact areas 34 represented inFig. 12. These relatively larger contact areas at the points of maximumload are very desirable and important because the load isdistributedover a considerably larger surface and wear of the parts isreduced to a minimum. That line contacts exist between the cam andfollower at the points 28 and 29 will be understood from the fact thatthe convex bearing portions 25 and 26 engaging the straight sides 2| and22 of the cam are substantially tangent to the straight sides and suchtangency produces a line contact. Likewise, it will be understood thatthe engagement of the convex bearing portions 25 and 26 with the concavesides of the cam at the points 3| and 32 produces an area of contactwhich is substantially wider than a line contact because the convex andconcave surfaces interfit more or less with each other. It will also beseen that centrifugal force acting on the followers l8 during therotation of the rotor I3 will press the bearing portions 25 and 26 ofthe follower against the sides 2| and 22 of the cam and may also pressthe cylindrical connecting portion 21 of the follower against the land23.

The cam I! shown in Figs. 1, 3, and 4 is a single-throw cam which,during one revolution of the rotor l3, will cause one forward and onereturn stroke of the follower l8. It will be readily seen, however, thatthe cam can be formed as a multi-throw cam which will produce two ormore complete strokes of the follower cooperating therewith. In Fig. 13of the drawings, I show a double-throw cam 35 formed on the innersurface of the cam sleeve 36. The cam 35 is similar to the cam H, but byreason of the fact that it is a multi-throw cam, it will have a sinuousshape rather than an elliptical shape, but its relatively narrowsections 3'! corresponding with the points of maximum load will stilllie in oblique or secant planes which intersect the rotation axis at thedesired angle of obliquity. The cam 35 will also impart simple harmonicmotion to its follower.

From the foregoing description and the accom 1 panying drawings, it willbe understood that the present invention provides a simple and efiicientconversion mechanism by which rotary motion can be converted toreciprocating motion or viceversa and which is well suited for use ineither i a pump, or in a hydraulic motor or engine.

Although the present invention has been illustrated and described inmore or less detail, there is no intention to limit the invention to thedetails and particular arrangements disclosed, but the invention isregarded as including all changes and modifications coming within thescope of the appended claims.

The above-described invention is claimed as follows:

1. In apparatus for converting rotary into reciprocating motion, a bodyhaving a plurality of axially slidable cam followers thereon, a sec--ond body substantially coaxial with the first body and having a camengaged by said followers, one of said bodies being adapted for relativerotation to produce reciprocation of said followers, said second bodybeing substantially cylindrical and said cam comprising an endless ridgehaving its base connected with said second axially slidable camfollowers thereon, a second body substantially coaxial with the firstbody and having a cam engaged by said followers, one of said bodiesbeing adapted for relative rotation to produce reciprocation of saidfollowers, said second body being substantially cylindrical and said camcomprising an endless ridge having its base connected with said secondbody and having alternate relatively wide and relatively narrow portionsof which the relatively narrow portions lie substantially in a secantplane of the cylindrical body and have concavely curved side wallsdiverging toward the base of the cam. said relatively wide portions ofthe ridge having substantially straight side walls diverging toward thebase of the cam, said curved and straight side walls of said relativelynarrow and relatively wide portions of the ridge being merged smoothlyinto each other.

3. In apparatus of the character described, a body having asubstantially cylindrical opening and an endless integral internal camgenerated on said body in the form of a ridge having its base connectedwith said body and comprising alternate relatively wide and relativelynarrow portions merging smoothly into each other and whose sides divergetoward the base of the cam.

4. In apparatus of the character described, a body having asubstantially cylindrical opening and an endless integral internal camgenerated on said body in the form of a ridge having its base connectedwith said body and comprising alternate relatively wide and relativelynarrow portions merging smoothly into each other, said relatively wideportions having substantially straight side walls diverging toward thebase of the cam and said relatively narrow portions having concave sidewalls diverging toward the base of the cam.

5. In apparatus of the character described, a body having asubstantially cylindrical opening and an endless integral internal camgenerated on said body in the form of a ridge having its base connectedwith said body and comprising alternate relatively wide and relativelynarrow portions merging smoothly into each other and whose sides divergetoward the base of the cam, and a reciprocating follower cooperatingwith said cam and having simple harmonic motion.

6. In apparatus of the character described, a body having asubstantially cylindrical opening and an endless integral internal camgenerated on said body in the form of a ridge having its base connected.with said body and corn-prising alternate relatively wide and relativelynarrow portions merging smoothly into each oth r, said relatively wideportions having substantially straight side walls diverging toward thebase of the cam and said relatively narrow portions having concave sidewalls diverging toward the base of the cam, and a reciprocating followercooperating with said cam and having simple harmonic motion.

7. In apparatus of the character described, a substantially cylindricalbody having thereon an endless cam ridge lying substantially in a secantplane and Whose base is connected with said body, and an axially movablecam follower having opposed substantially frusto-conical bearingportions arranged to straddle the cam ridge and engage the side facesthereof, said cam ridge having alternate relatively narrow andrelatively wide portions merging smoothly with each other, saidrelatively wide portions having substantially straight side facesdiverging toward the base of the cam and with which said bearingportions have substantially a line contact and said relatively narrowportions having concave side faces diverging toward the base of the camand with which said bearing portions have contact of greater area than aline contact.

8. In apparatus of the character described, a substantially cylindricalsleeve having an integral internal endless cam ridge thereon lyingsubstantially in asecant plane and whose base is connected with saidsleeve, and a rotatable body having thereon an axially slidable camfollower provided with opposed substantially frustoconical bearingportions arranged to straddle the cam ridge and engage the side facesthereof, said cam ridge having alternate relatively narrow andrelatively wide portions merging smoothly with each other, saidrelatively wide portions having substantially straight side facesdiverging toward the base of the cam and with which said bearingportions have substantially a line contact and said relatively narrowportions having concave side faces diverging toward the base of the camand with which said bearing portions have contact of greater area than aline contact.

9. In apparatus of the character described, a substantially cylindricalbody having thereon an endless cam ridge lying substantially in a secantplane and whose base is connected with said body, and an axially movablecam follower having opposed substantially frusto-conical bearingportions arranged to straddle the cam ridge and engage the side facesthereof, said cam ridge having alternate relatively narrow andrelatively Wide portions merging smoothly with each other, saidrelatively wide portions having substantially straight side facesdiverging toward the base of the cam and with which said bearingportions have substantially a line contact and said relatively narrowportions having concave side faces diverging toward the base of the camand with which said bearing portions have contact of greater area than aline contact, said relatively wide portions of the cam ridge beingrelatively closer to the ends of said sleeve than said relatively narrowportions and said relatively narrow portions being substantially midwaybetween said relatively wide portions.

10. In apparatus for converting rotary into reciprocating motion, a bodyhaving a plurality of axially slidable cam followers thereon, a secondbody substantially coaxial with the first body and having a cam engagedby said followers, one of said bodies being adapted for relativerotation to produce reciprocation of said followers, said second bodybeing substantially cylindrical and said cam comprising an endless ridgehaving its base connectedwith said second body and having alternaterelatively wide and relatively narrow portions of which the relativelynarrow portions lie substantially in a secant plane of the cylindricalbody and have concavely curved side walls diverging toward the base ofthe cam, said followers being cylindrical members havingcircumferentially grooved portions in rolling contact with said cam.

11. In apparatus for converting rotary into reciprocating motion, a bodyhaving a plurality of axially slidable cam followers thereon, a secondbody substantially coaxial with the first body and having a cam engagedby said followers, one of said bodies being adapted for relativerotation to produce reciprocation of said followers, said second bodybeing substantially cylindrical and said cam comprising an endless ridgehaving its base connected with said second body and having alternaterelatively wide and relatively narrow portions of which the relativelynarrow portions lie substantially in a secant plane of the cylindricalbody and have concavely curved side walls diverging toward the base ofthe cam, said relatively wide portions of the ridge having substantiallystraight side walls diverging toward the base of the cam, said curvedand straight side walls of said relatively narrow and relatively wideportions of the ridge being merged smoothly into each other, saidfollowers being cylindrical members having circumferentially groovedportions in rolling contact with said cam and having their axes parallelto the common axis of said first and second bodies.

12. In apparatus of the character described, a body having asubstantially cylindrical opening and an endless integral internal camgenerated on said body in the form of a ridge having its base connectedwith said body and comprising alternate relatively wide and relativelynarrow portions merging smoothly into each other and whose sides divergetoward the base of the cam, and a, reciprocating cylindrical followerhaving a circumferentially grooved portion in rolling contact with saidcam.

V 13. In apparatus of the character described, a substantiallycylindrical body having thereon an endless cam ridge lying substantiallyin a secant plane and whose base is connected with said body, and anaxially movable cylindrical cam follower in rolling contact with the camridge and having opposed substantially frusto-conical bearing portionarranged to straddle the cam ridge and engage the side faces thereof,said cam ridge having alternate relatively narrow and relatively wideportions merging smoothly with each other, said relatively wide portionshaving substantially straight side faces diverging toward the base ofthe cam and with which said bearing portions have substantially a linecontact and said relatively narrow portions having concave side facesdiverging toward the base of the cam and with which said bearingportions have contact of greater area than a line contact.

JETTA TRUESDELL. Administratrz'a: of the Estate of Fred A. Truesdell,

Deceased.

